Method of removing scale from heating apparatus for pulp-digesters.



. 75. Momma] METHOD OFk REMOVKNG SCALE FROM HEATING APPARAT f kAPFUCANN FILED AUG. 5 Z914;

Us Fon PULMPDIGESKTERS.

M991,451.` mm .my 1g, 1916.

Figi n l uNrrED sTATEs PATENT OFFICE.

- EINAR MQRTERUD, oF JELN, NORWAY.

METHD OF REMOVING SCALE FROM HATIN G lAPIE'ARA'JIUS FOR PUL-DGESTESV':

-To /il 11j/tom. t 17u73/ concern.'

Be it known that L-Eixaii ,l\I(iii1uiiUii,` a' subject ot the King' of Norway, residing at scription oi the invention, such as will en`` able others skilled inthe -art to which it appertains to iiiake and use the saine.`

My inrentioii relates to the iiiaiiuracture oi pulp or cellulose a method t'or removing the` incrustation or scale toi-ined on the tubes and other devices used in apparatustor heatiiigthe solution with which `the pulp digesters are supplied. VWhen using' the indirect system oheating the solution the said ioriii'ation of scale or incrustation is very.detrimental inasmuch as it prevents the transfer oi heat.

According' to uiy invention the seale on the outside ot tiilies ,may be removed in the following' iiiaiiiier. heii the tubes mounted in a heating' apparatus for pulp digester.solution and serving' .to.heat the saine 'by way of'steaiii or hot water passiiipr through the tube. have been covered b v iiiciustation or scale toa certain thickness, lf sluit olf the heating apparatus t'ioiii the digester and discharge the solution so that the heating' apparatusis empty. I then pass steam through the tubes so as to remove the moisturev from the scale `and iiiake it pericectly dry. By suchy procedure the tube and the scale thereon will belieated to a somewhat higher temperature than the temperature to which they are heated during the digesting' process. because the tube'- is then cooled by the circulating solution. Therefore the. tube and tliejsealewill attain a greater diameter during the jdryimgr process and lthe tubular covering of scale will thereby be ruptured.

When 'the scale is perfectly dry I sliut'otf the steam or hot water supplyr to the tubes and cool the tubes rapidly for instance by passing cold water through them. When this is done iii a. suliiciently rapid way the tubes will be cooled more than the scale sui'- .reason this tubular covering ol' scale will looseir from theIv metal tubesl which rapidly contract;

while the scale tubes remainl about ol the saine diameter; when the scale has iii this troni AHeating' Apparatus tor do hereby declarethe and more ,especially-to Aprises a heating drum l` provided is supplied to the. tubes Specification of Letters Patent.

.1);1teiiteti-Jaiy'1s, 1916."

Application filed August'6,1914. SerialNo.855,448.` v

`manner loosenedt'romtlie tubes it Vmay 'easily be knocked ofi' or will fall ofi of itself. I

T may also preferably `carry out thegiiifst `part ot' the method iii the wayr that the drying' of the scale is performed by way of a iii'ore gentle heating, lfor. instance by-steam .ot somewhat more than 100. centigiade.

which is below the temperature atwliich the, scale is formed. Thereupon steam' of high temperature, say lfce'ntigrade. is passed the `temperature lat which the scale is formed causing,` as above described, the bursting` of the scale.y i y J l i In the accompanying (flr'awiiigfFigure;1 is an elevation, partlyiii section lof appara- `ti`isforheating digesting fluid and in which sel i through the tubes to heat the latter above iny method may be carried out. Fig. 2 is i i an enlarged transverse sectional view of onel set of the heating tubes, tube, which comes into contact with tlie`di gesting fluid, covered with scale. Fig. 3y is a4 likeview showing the scale cracked.

. The heating apparatusyhere shown coniwithY a plurality ot' ,vertical tubes 2 one of which is shown in the drawing). These tubes are closed at the top "and ar arranged to be sui*- rounded by the digesting solution which is supplied tothe drum through :1.-pipe`3 and conveyed to a digester (not shown) through a pipe 4 at the top of the drinn.`

chamber 5 into from the steam used in heating the tubes passes and4 is'drawn ofi Athrough pipe 6. The steam, or hot water, used as a heating me diuni is supplied from a steam or hot Water pipe 7 to a chamber 8 from which priser pipes 9 extend into the tubes to near the tops ot' the latter. vThe riser pipesbeingopen at their` upper ends'steam or .water will iiow i therefrom, down betweentlie'said pipes 9 and tubes 2 into the 'chamber 5.

Air `that assembles in the, tubes 2 may be drawn ott' from time to time through pipes lOvwhicli extend from. a chainberll through the upper open ends of the pipes 9; vancoutlet yfrom the chamber 11 being controlled by aV valved pipe` 12.

When the tubes 2 become covered 'with tion is drained from the drum l, and steam 2, until tlieyexpand si'iticiently to rupture the scale.

showing the outerf' Said tubes i '.coininunicate at their lower ends withI a.

which water of condensation The supply of steam is then shut oil' by means of-the cook 7 in the steam pipe 7 and cold water is then supplied from a pipe 13 to the tubes 2 to rapidly contract them.

I claim- 1. The method of removing scale from the outside of 4heating tubes in pulp digesters and the like, which method comprises first drying the scale by heating the tubes to a temperature below the temperature at which the scale is formed, subjecting the tubes to a temperature above the ltemperature at (which the` sealeis formed, and suddenly cooling the tubes to a temperature below either of the aforesaid temperatures.

2. A method of removing incrustation or scale from the outside of heating tubes and the like in heating apparatus for solutions W t. used in 1mlp digestcrs and the like compris- -29 lution from the apparatus, passing a heating medium through the tubes to dry the scale ing the -ollowing steps: discharging 'the so by a moderate heat, passing a heating I'nedium of very high temperature through the tubes to heat the tubes to a higher ternperature than that to which they are heated during the digesting process, and finally passing a cooling?r medium through the tubes so as to oa11se' rapid'cooling and contraction of the tubes, thereby loosening,lr the` scale from the tubes so it may be knocked oil'.

3. The method of removing scale from the outside of heating tubes in pulp digesters and the like, which niethod consists in removing the digesting solution from in Contact with the tubes gradually drying the scale by passing steam through the tubes, subsequently passing steam of very high temperature through the tubes to increase the temperature of the tubes above that to which they are healed during the (.ligesting` process, thereby expanding?r the tubesand si multaneously rupturng the scale, and iinally passingr cold water through the tubes to rapidly cool and contract them.

In testimony that I elaixn the foregoing as my inventiom have signed my name in presence of two subscribing witnesses.

l EINAR IVIORTERUD.

Witnesses:

RUTH LINDSTRN, CoNs'rA'soE F. HANSEN. 

